Thread-cutting tap.



C. SCHOENERT.

THREAD CUTTING TAP.

APPLICATION FILED JAN-18.1917.

1,232,099. Patented July 1017.

2 SHEETSSHEET l- Fy] fyi fizve' 61 1/24 Shady/5R7:

C. SCHOENERT.

THREAD CUTTING TAP.

APPLICATION FILED JAN. 18, 1917.

1,232,099. Patented July 3, 1917.

2 SHEETS-SHEET 2 F 94 figr f CARL SCHOENERT, OF NEWARK, NEW JERSEY.

THREAD-CUTTING TAP.

Specification ofLetters JPatent.

Patented July a, 1911?.

Application filed January 18, 1917- Serial No. 143,169.

number of lengthwise slots extending to or beyond the region of the thread, and these slots become rapidly clogged with cuttings, and in order to prevent the thread being marred by the cuttings the tap must be screwed out from time to time and cleaned,-

and to make a satisfactory thread considerable time and trouble is required, particularly in the case of tapping holes of a large diameter. Also it is frequently necessary to make use of a series of taps of such ordinary construction in multiple, one after another, in order to obtain a sharp and properly defined thread, especially when tapping holes of comparatively large diameter. When such solid taps break oif in use, as they frequently do, their removal is a matter of extreme difliculty.

According to the present invention a tap is provided having a hollowed out central portion or bore whereby the tap is stren hened, and it also becomes possible to tea ily remove it, if it should be broken ofi, by

means of suitable tools introduced into the" the entering of t e tap into the hole whic is to be threaded. When the central bore is provided in taps in accordance with my invention, 'the same may be obtained in any suitable way, as by drilling solid stock or by making use of hollow taps from which the edge may be constructed, or in other ways. The cutting away of the bore in least a part of the tap does not extend as far as the center thereof, so that the fitting of the tap in place in the opening is not interfered with and the threads obtain a good cutting action against the material on the sides of the openlng of the bore. The cutting away may be all along one side or may be of other forms, as, for example, the

cut away portion of the tap may be of spiral.

form or variousother forms, but is preferably so carried out as to bring each cutting tooth somewhat out of line with the preceding cutting tooth or thread, whereby the cutting action advances or retreats substantially on an incline, thereby greatly reducing the danger of tap breakage and giving greater ease of operation.

With the foregoing and related objects in view, my invention consists in the features of construction and improvement herein set forth and claimed. v

In the accompanyin drawings I have illustrated, for the purpose of making my invention clearly understood and not for the purpose of limitation, however, three forms of taps in which my invention may be embodied. In the said drawings, Figure 1 is aside view of one form of tap embodying my invention. Fig. 2 is another side view of the same tap takenat right angles to Fig. 1. Fig. 3 is a cross-sectional view taken on the line 33, Fig. 1. Fig. 4 is a side view of another form of tap embodying mfy invention; Fig. 5 is a second side view 0 the tap shown in Fig. 4 and taken at ri ht angles thereto. Fig. 6 is a side view 0 a third form of tap embodying my invention,

and Fig. 7 is a secondside view of the tap shown 1n Fig. 6 and taken at'right angles thereto.

Numeral 10 designates the shank of the tap and 11 thev customary square head by means of which power may be applied to turn the tap, it being understood, of course, that other means for rotatin V be resorted to. 12 indicates t e hollow bore of the tap and 13 threads formedthereon which, as is usual, are shortened or out 0d at the entering end of the tap. in the form shown in Figs. 1 and 2 a substantially spiral cut away portion 14 is provided, forming an o ening of substantially spiral character along one side of the ta and communicating with the hollow interlor 12. The cutting edges 15, if desired, may be made progressively sharper toward the top of the ten,

the tap may opposite edge 17 the cutting action,

or, in other words, the under cut may be increased, so that the cut is finished with the sharpest pointed teeth and is begun with teeth which are relatively dull or notso sharply pointed.

In the tap shown in Figs. 1 and 3, when cutting right hand threads the cutting edge is represented at 15, and this. edge is cut back at an angle, as indicated at 16, so as to provide a sharp under cut cutting edge for the points or teeth of the thread 13'whereby an eflicient cutting action is obtained. The is shown as projecting somewhat on the interior instead of being under cut, but the precise form of this edge is not important, except that it is preferably so designed as to give as great strength as possible. This substantially spiral cut in the diemay be readily formed, as, for example, by'a milling machine.

In. Figs. 4 and 5 the tap 20 has a central bore 21, and the cut away portion 22 thereof is all on one side. In this form the cut away 22 is provided by forming substantially scalloped portions comprising alternate projecting parts 23 and recessed parts 24, the scallops extending substantially directly across the tap at right angles to the longitudinal axis thereof, and-the cutting away or scalloping of the tap not'being extended in at least a portion of its length entirely through the median line thereof, whereby the proper location of the tap in the hole to be threaded is not interfered with. In this way the cutting edge gradually advances and retreats as the ta cuts deeper, so that the cutting action is a ways more or less on an incline.

In Figs. 6 and 7 the tap 30 has a bore 31, and the tap of these figures is similar to that of Figs. 4 and 5, except that the scalloped portions 32 are formed at an" angle to the longitudinal axis of the tap other than a right angle. This preciSe angle may, of course, vary fromlthat shown.

The operation ofa tap in accordance with my invention will be readily1nnderstood from the foregoing. Being introduced'in a hole to be threaded in the ordinary way, it may be readily screwed down," and with one passage a sharply defined thread ob tained, the cuttings dropping outi as fast as they are formed and not interfering with very little power being making .the""cut, the use of.

required for v to secure a sharp thread is no multiple taps threaded cutting surface and exterior surface,

longer requisite, and the taps so constructed are very strong and will scarcely ever break ofi, and if they should it is readily possible to remove the same by means of a proper 001 which may be inserted in the central ore.

It is to be understood that the forms illustrated are for the purpose of affording a clear understanding of my invention only, and that I am not to be confined to such specific form or forms, but that numerous changes therein and departures therefrom may be resorted to within the scope of my claims and without departing from or sacrificing any of the advantages of my invention.

What is claimed is:

1. A tap having a hollow bore and provided with an elongated cut away part extending from the bore to the exterior of the tap and providing cutting teeth at one edge of the cut away part.

2. A thread tap having a hollow bore and a cut away part extending throughout the length of the threaded portion.

3. A tap having a threaded exterior wall, the threads. being continuous except on one side of the tap where the material thereof is cut away, the cut away extending 1nwardly and including the longitudinal axis of the tap.

4. A tap provided with an exterior with a hollow interior bore, the material. of the tap being cut away from the bore to the exterior thereof along substantially a spiral line.

5. In a tap, a threaded exterior cutting surface,an interior hollow bore, said tap being cut away from the bore to its exterior and providing forwardly inclined sharp cutting teeth on the cutting edge of the tap.

6. In a tap, surface, an interiorhollow bore extending into theshank beyond the threaded surface, said tap. beingcut away from the bore to its said cut away being on an angle onthe. cutting side of the tap whereby the cutting teeth have sharp penetrating points.

7. A tap provided with an outer threaded surface and; a hollow bore, and being cut away to the bore on one side, the cut away part providing cutting teeth arranged at an angle to the longitudinal axis of the tap.

In testim'ony whereof I'aflix 'my signature.

CARL SCHOENERT.

'a threaded exterior cutting 

